Replace by position

replace_comp.R

## Context: https://twitter.com/grant_mcdermott/status/1249825585175523328

set.seed(123)
m = matrix(1:10000000, ncol = 1000)

x_pos = sample.int(nrow(m), size = nrow(m)/2)
y_pos = sample.int(ncol(m), size = ncol(m)/2)
m_pos = (y_pos-1)*nrow(m) + x_pos

library(data.table)
d = as.data.table(m)


library(microbenchmark)

f1 = function(val) {
  m[x_pos, y_pos] = val
}

f2 = function(val) {
  replace(m, m_pos, val)
}

f3 = function(val) {
  d[x_pos, y_pos] = val
}

microbenchmark(f1("a"), f2("a"), f3("a"), times = 10)

# Unit: milliseconds
#     expr        min         lq       mean     median         uq        max neval cld
#  f1("a") 1763.69864 1875.60289 2437.56736 2205.15627 2622.15864 4090.56228    10   b
#  f2("a") 1713.88150 1861.22836 2167.71451 2139.27080 2264.02732 2870.44860    10   b
#  f3("a")   34.73604   35.17439   36.47502   35.31709   36.22141   45.15878    10  a